The central nervous system (CNS) is the processing center for the nervous system. CNS disorders can affect the brain, the spinal cord, and nerve endings, resulting in neurological and/or psychiatric disorders. CNS disorders can be caused by genetic inheritance, trauma, infection, autoimmune disorders, structural defects, tumors, and stroke. Certain CNS disorders are characterized as neurodegenerative disease, many of which are inherited genetic diseases. Examples of neurodegenerative diseases include Huntington's disease, ALS, hereditary spastic hemiplegia, primary lateral sclerosis, spinal muscular atrophy, Kennedy's disease, Alzheimer's disease, a polyglutamine repeat disease, or Parkinson's disease. Treatment of CNS disorders, e.g., genetic diseases of the brain such as Parkinson's disease, Huntington's disease, and Alzheimer's disease, remain an ongoing problem.
Alzheimer's disease is a common form of age-related dementia that causes gradual loss of cognitive function, including memory and critical thinking abilities. Alzheimer's disease is diagnosed clinically by through a finding of progressive memory loss and decrease in cognitive abilities. However, confirmation of Alzheimer's disease does not occur until after death.
Alzheimer's disease is becoming more prevalent in developed nations, where an increase in the population of elder persons has occurred due in part to improved healthcare. While less than 1% of the population under the age of 60 is affected by Alzheimer's, it is estimated that 25% to 33% of persons develop some form of Alzheimer's by the age of 85. As of 2012, 5.4 million Americans were diagnosed with Alzheimer's. As life expectancy continues to increase worldwide, the prevalence of Alzheimer's and other age-related dementia should continue to grow as well.
Alzheimer's disease is typically classified as either “early onset,” referring to cases that begin to manifest at between 30 and 60 years of age in affected individuals, and the more common “late onset” Alzheimer's, in which symptoms first become apparent after the age of 60. Although only about 10% of all Alzheimer's cases are familial, early onset Alzheimer's disease has been linked to mutations in the amyloid precursor protein (app), presenilin 1 (psen1), and presenilin 2 (psen2) genes, while late onset Alzheimer's disease has been linked to mutations in the apolipoprotein E (apoE) gene (Ertekin-Taner N., Neurol Clin., 25:611-667 (2007)).
Histopathologically, this neurodegenerative disease is characterized by the formation of amyloid plaques, neurofibrillary tangles, amyloid angiopathy, and granolovacuolar degeneration in the cerebral cortex (Mirra et al., Arch Pathol Lab Med., 117:132-144 (1993); Perl D P, Neurol Clin., 18:847-864 (2000)). The characteristic amyloid plaques, used to confirm Alzheimer's disease post-mortem, are formed largely by deposition of a small amyloid-beta (Aβ) peptide derived from the amyloid precursor protein (APP).
To date, the U.S. Food and Drug Administration (FDA) has approved two types of medications for the management of Alzheimer's disease: cholinesterase inhibitors, including donepezil (e.g., ARICEPT®), rivastigmine (e.g., EXELON®), galantamine (e.g., RAZADYNE®), and tacrine (e.g., COGNEX®); and the NMDA-type glutamate receptor inhibitor memantine (marketed under a number of different brands). Although a cure for Alzheimer's disease has not been identified, these therapies serve to alleviate cognitive symptoms such as memory loss, confusion, and loss of critical thinking abilities in subjects diagnosed with age-related dementia (e.g., Alzheimer's disease). In all, it is estimated that healthcare spending on Alzheimer's disease and related age-related dementias in 2012 will be $200 billion in the United States alone (Factsheet, Alzheimer's Association, March 2012).
In addition to these approved therapies, several studies have suggested that pooled intravenous immunoglobulin (IVIG) is effective in slowing the progression of symptoms in Alzheimer's patients (Dodel R C et al., J Neurol Neurosurg Psychiatry, Oct; 75(10):1472-4 (2004); Magga J. et al., J Neuroinflammation, December 7; 7:90 (1997); Relkin N R et al., Neurobiol Aging, 30(11):1728-36 (2008); Puli L. et al., J Neuroinflammation May 29; 9:105 (2012)).
Immune globulin products from human plasma were first used in 1952 to treat immune deficiency. Initially, intramuscular or subcutaneous administration of immunoglobulin isotype G (IgG) isolated from plasma were the methods of choice. However, IgG products that could be administered intravenously, referred to as intravenous immunoglobulin (IVIG), were later developed to allow for the administration of larger amounts of IgG necessary for effective treatment of various diseases. Usually, IVIG contains the pooled immunoglobulin G (IgG) immunoglobulins from the plasma of multiple donors, e.g., more than a hundred or more than a thousand blood donors. These purified IgG products are primarily used in treating three main categories of medical conditions: (1) immune deficiencies: X-linked agammaglobulinemia, hypogammaglobulinemia (primary immune deficiencies), and acquired compromised immunity conditions (secondary immune deficiencies), featuring low antibody levels; (2) inflammatory and autoimmune diseases; and (3) acute infections.
Specifically, many people with primary immunodeficiency disorders lack antibodies needed to resist infection. In certain cases these deficiencies can be supplemented by the infusion of purified IgG, commonly through intravenous administration (i.e., IVIG therapy). Several primary immunodeficiency disorders are commonly treated in the fashion, including X-linked agammaglobulinemia (XLA), Common Variable Immunodeficiency (CVID), Hyper-IgM Syndrome (HIM), Severe Combined Immunodeficiency (SCID), and some IgG subclass deficiencies (Blaese and Winkelstein, J. Patient & Family Handbook for Primary Immunodeficiency Diseases. Towson, M D: Immune Deficiency Foundation; 2007).
While IgG treatment can be very effective for managing primary immunodeficiency disorders, this therapy is only a temporary replacement for antibodies that are not being produced in the body, rather than a cure for the disease. Accordingly, patients depend upon repeated doses of IgG therapy, typically about once a month for life. This therapy places a great demand on the continued production of IgG compositions. However, unlike other biologics that are produced via in vitro expression of recombinant DNA vectors, IgG is fractionated from human blood and plasma donations. Thus, the level of commercially available IgG is limited by the available supply of blood and plasma donations.
Several factors drive the demand for IgG, including the acceptance of IgG treatments, the identification of additional indications for which IgG therapy is effective, and increasing patient diagnosis and IgG prescription. Notably, the global demand for IgG more than quadrupled between 1990 and 2009, and continues to increase at an annual rate between about 7% and 10% (Robert P., Pharmaceutical Policy and Law, 11 (2009) 359-367). For example, the Australian National Blood Authority reported that the demand for IgG in Australia grew by 11.1% for the 2010-2011 fiscal year (National Blood Authority Australia Annual Report 2010-2011).
It has been reported that in 2007, 26.5 million liters of plasma were fractionated, generating 75.2 metric tons of IgG, with an average production yield of 2.8 grams per liter (Robert P., supra). This same report estimated that global IgG yields are expected to increase to about 3.43 grams per liter by 2012. However, due to the continued growth in global demand for IgG, projected at between about 7% and 14% annually between now and 2015, further improvement of the overall IgG yield will be needed to meet global demand. One of the factors that may drive increased demand for pooled human immunoglobulins (e.g., IVIG) over the next decade is whether or not IgG is approved for the treatment of Alzheimer's disease. It is estimated that if these treatments are approved by major regulatory agencies, an additional 5% increase in demand for IVIG will be seen (Robert P., supra).
Due in part to the increasing global demand and fluctuations in the available supply of immunoglobulin products, several countries, including Australia and England, have implemented demand management programs to protect supplies of these products for the highest demand patients during times of product shortages. Thus, the development of methodologies that reduce the amount of pooled immunoglobulin G needed to treat various indications will be critical as the increase in demand for pooled immunoglobulin begins to outpace the increase in global manufacturing output.
Pooled human immunoglobulin G (IgG) is manufactured according to different processes depending upon the specific manufacturer. However, the origin of most manufacturing processes is found in the fourth installment of a series of seminal papers published on the preparation and properties of serum and plasma proteins, Cohn et al. (J. Am. Chem. Soc., 1946, 68(3): 459-475). This paper first described a method for the alcohol fractionation of plasma proteins (method 6), which allows for the isolation of a fraction enriched in IgG from human plasma.
The Cohn procedures were initially developed to obtain albumin at relatively high (95%) purity by fractional precipitation with alcohol. However, it was realized by Oncley et al. (J. Am. Chem. Soc., 1949, 71(2): 541-550), Deutsch et al. (J. Biol. Chem., 1946, 164, 109-118), and Kistler and Nitschmann (Vox Sang., 1962, 7, 414-424), that particular protein precipitates (Fraction II and Fraction II+III) from the Cohn method could be used as a starting material for the purification of highly enriched immunoglobulin compositions. In order to achieve the higher purity and safety required for the intravenous administration of IgG compositions, several purification and polishing steps (e.g. adsorption in general or all different chromatographic techniques, Cross-flow-filtration, etc.) have been added to IgG manufacturing processes after the alcohol fractionation steps.
Current IgG manufactures typically rely on either a Cohn method 6 Fraction II+III precipitate or a Kistler-Nitschmann precipitate A as the starting material for downstream processing. Both fractions are formed by a two step process in which proteins such as fibrinogen and Factor XIII are removed by an initial precipitation step (Fraction I precipitation) performed at high pH (7.2) with low ethanol concentration (8-10% v/v), followed by a second precipitation step in which IgG is precipitated from the Fraction I supernatant at pH 6.8 with 20-25% (v/v) ethanol (Fraction II+III) or at pH 5.85 with 19% ethanol (v/v) ethanol (precipitate A), while albumin and a significant portion of A1PI remain in the supernatant.
These methods, while laying the foundation for an entire industry of plasma derived blood proteins, were unable to provide IgG preparations having sufficiently high purity for the chronic treatment of several immune-related diseases, including Kawasaki syndrome, immune thrombocytopenic purpura, and primary immune deficiencies, without an undue occurrence of serious side effects. As such, additional methodologies employing various techniques, such as ion exchange chromatography, were developed to provide higher purity IgG formulations. Hoppe et al. (Munch Med Wochenschr 1967 (34): 1749-1752), Falksveden (Swedish Patent No. 348942), and Falksveden and Lundblad (Methods of Plasma Protein Fractionation 1980) were among the first to employ ion exchange chromatography for this purpose.
It is common practice to administer IgG by intravenous (IV) injection (Imbach et al., Lancet 1(8232): 1228-31 (1981)). Intravenous IgG (IVIG) may be administered alone or in combination with other compositions. IVIG is often administered over a 2 to 5 hour period, once a day for 2 to 7 days, with follow-up doses every 10 to 21 days or every 3 to 4 weeks. Such an administration regime is time consuming and inconvenient for many patients. This inconvenience may be aggravated in the case of Alzheimer's patients, who may have difficulty sitting quietly during the infusion period, and may have to rely on their caregiver to bring them to an infusion center or supervise their infusion.
Systemic IVIG administration may cause adverse side effects. For example, IVIG may cause backache, headache, migraine, joint or muscle pain, general feeling of discomfort, leg cramps, rash, pain at the injection site, hives, dizziness, unusual fatigue or tiredness or weakness, chills, fever, sweating, increased heart rate, increased blood pressure, cough, redness of the face, upset stomach, upper abdominal pain, and vomiting. Immediate adverse effects post-IVIG administration which have been observed include headache, flushing, malaise, chest tightness, fever, chills, myalgia, fatigue, dyspnea, back pain, nausea, vomiting, diarrhea, blood pressure changes, tachycardia, and anaphylactic reactions. Orbach et al., Clin. Rev. Allergy Immunol., 29(3): 173-84 (2005).
Furthermore, the adverse side effects may vary based on the IVIG manufacturer. Most manufactures preparations contain between 90% and 99% purified IgG in combination with stabilizers and liquid(s) for reconstitution. Orange et al. 2006 (J. Allergy Clin. Immunol. 117(4 Suppl.): S525); Vo et al. 2006 (Clin. J. Am. Soc. Nephrol. 1(4): 844; Stiehm et al. 2006 (J. Pediatr. 148(1): 6). For example, some manufacturers use maltose as a stabilizer while others use sucrose or amino acids.
The sodium and sugar content in WIG, along with varying amounts of IgA and additional chemicals used in the IVIG production can affect the tolerability and efficacy of the brand of IVIG in patients. Specifically, older patients often suffer from co-morbid conditions that increase the risk of IVIG adverse side effects. For example, subjects with renal disorders, vascular disorders, or diabetes also have a heightened risk of renal insufficiency and thrombotic events following IVIG administration because IVIG compositions are commonly hyper-viscous and contain high concentrations of sugar and salt.
IVIG also carries the risk of catheter-related infection, i.e., an infection where the catheter or needle enters a subject's vein or skin. Examples of catheter-related infection are tenderness, warmth, irritation, drainage, redness, swelling, and pain at the catheter site. Accordingly, alternate modes of administration would be beneficial from the standpoint of time, convenience, and adverse side effects.
In addition to adverse side effects of systemic administration of IVIG, penetration of IVIG across the blood-brain barrier has been shown to be unpredictable and intraventricular or intrathecal IgG may be necessary. For example, Haley et al. administered IVIG in the treatment of meningeal inflammation caused by West Nile virus encephalitis. Haley et al. found that penetration of IVIG was unpredictable and posited that intrathecal or intraventricular administration may be required. Haley et al. 2003 (Clin. Inf. Diseases 37: e88-90).
It is difficult to target the CNS with IV administration therapeutic compositions because of the blood-brain barrier (BBB). The BBB provides an efficient barrier, preventing and/or limiting access to the CNS of therapeutic compositions administered intravenously into the peripheral circulation. Specifically, the BBB prevents diffusion of most therapeutic compositions, especially polar compositions, into the brain from the circulating blood.
At least three methods for increasing the passage of molecules through the BBB have been developed. First, lipophilic compounds such as lipid-soluble drugs and polar drugs encased in a lipid membrane have been developed. Lipophilic compounds with a molecular weight of less than 600 Da can diffuse through the BBB. Second, therapeutic compounds can be bound to transporter molecules which can cross the BBB through a saturable transporter system. Examples of saturable transporter molecules are transferrin, insulin, IGF-1, and leptin. Third, therapeutic compounds can cross the BBB by binding the therapeutic compounds to polycationic molecules such as positively-charged proteins that preferentially bind to the negatively-charged endothelial surface of the BBB. Patridge et al. 2003 (Mol. Interv. 3(2): 90-105); Patridge et al. 2002 (Nature Reviews-Drug Discovery 1:131-139). However, each of the above-described approaches for increasing the delivery of therapeutics through BBB to gain access to the CNS are limited. One such limitation is that the above-described approaches rely on systemic delivery systems, e.g., administration directly or indirectly to the blood stream, which results in non-specific delivery of the therapeutic agent to other parts in the body, increasing the chance of adverse side effects.
Intranasal administration of therapeutics has become an increasingly explored method for delivering therapeutic agents to the brain because it circumvents the BBB and is a localized, non-invasive method for delivery. Furthermore, intranasal administration offers the advantages, over more traditional methods of delivery (e.g., intravenous, subcutaneous, oral transmucosal, oral or rectal administration), of being simple to administer, providing rapid onset of action, and avoiding first-pass metabolism. Unfortunately, intranasal administration has only been shown effective for the transport of small molecules, and to a certain extent smaller Fc fusion proteins, to the brain. The delivery of larger molecules, such as intact antibodies, has not yet been demonstrated. The difficulty in transporting larger proteins is believed to be due to the limited permeability of tight junctions present in the olfactory epithelia, which likely excludes globular molecules having a hydrodynamic radius of more than 3.6 Å (Stevenson B R, et al., Mol Cell Biochem., 1988 October; 83(2):129-45).
U.S. Pat. No. 5,624,898 to Frey describes compositions and methods for transporting neurologic agents, which promote nerve cell growth and survival or augment the activity of functioning cells, to the brain by means of the olfactory neural pathway. The neurological agents of the '898 patent are transported to the brain by means of the nervous system, rather than the circulatory system, so that potentially therapeutic agents that are unable to cross the blood-brain barrier may be delivered to damaged neurons in the brain. The compositions described in the '898 patent include a neurologic agent in combination with a pharmaceutical carrier and/or additive which promote the transfer of the agent within the olfactory system. The '898 patent does not teach intranasal administration of pooled human immunoglobulins.
PCT publications WO 2006/091332 and WO 2009/058957, both by Bentz et al., describe methods for the delivery of therapeutic polypeptides to the brain by fusing the polypeptide to an antibody or antibody fragment and administering the resulting fusion protein intranasally. Although the examples of the '332 and '957 PCT publications suggest that Fc-fusion “mimetibodies” may be administered intranasally, neither publication demonstrates delivery of larger, intact antibodies. In fact, the '957 PCT publication, published three years after the '332 PCT publication, states that “[i]n published delivery studies to date, intranasal delivery efficiency to the CNS has been very low and the delivery of large globular macromolecules, such as antibodies and their fragments, has not been demonstrated.” The '957 PCT publication purports to solve this problem through the use of a permeability enhancer (e.g., membrane fluidizers, tight junction modulators, and medium chain length fatty acids and salts and esters thereof, as described below), which enhances intranasal administration to the central nervous system. Neither PCT publication teaches intranasal administration of pooled human immunoglobulins.
PCT publication WO 2003/028668 by Barstow et al., describes the treatment of immune-mediated diseases by alimentary administration (i.e., administration to the digestive tract) of pooled immunoglobulins. Although the '668 PCT publication discloses nasal administration of a composition of pooled immunoglobulins, it is in the context of delivering the composition to the digestive tract. The '668 PCT publication does not teach the delivery of pooled human immunoglobulins to the brain via intranasal administration.
PCT publication WO 2001/60420 by Adjei et al., describes aerosol formulations of therapeutic polypeptides, including immunoglobulins, for pulmonary delivery. These aerosolizable compositions are formulated such that after oral or nasal inhalation, the therapeutic agent is effectively delivered to the patient's lungs. The '420 PCT publication does not teach the delivery of therapeutic agents to the brain via intranasal administration.
Accordingly, there is a need in the art for methods of treating central nervous system disorders, such as Alzheimer's disease, using pooled human immunoglobulin G that provide specific targeting to the CNS (e.g., administration primarily to the brain), reduce systemic distribution of the pooled immunoglobulins, and lower the therapeutically effected dose needed for administration.